1. Technical Field
This application claims the benefit of Japanese Patent Application No. 2004-335590, filed Nov. 19, 2004. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety.
This invention relates to a method for forming a wiring pattern, a method for manufacturing a device, a device, an electro-optic apparatus, and electronic equipment.
2. Related Art
A photolithography method, for example, is used for manufacturing a device including wiring in use for electronic circuits or integrated circuits. In the photolithography method, a photosensitive material called a resist is applied to a substrate on which a conducting film is formed beforehand, a circuit pattern is irradiated with light for exposure and development, a conducting film is etched in accordance with the resist pattern, and as a result, a wiring pattern of a thin film is formed. The photolithography method requires large-scale equipment such as a vacuum device and complicated processes, and also has a material use efficiency of about several percent such that most of materials have to be discarded, thereby leading to high manufacturing costs.
A method of forming a line pattern on a substrate by using a droplet discharge technique in which a functional liquid, which is a liquid material, is discharged in a droplet from a droplet discharge head is proposed, for example, as disclosed in U.S. Pat. No. 5,132,248, which is an example of related art. In this method, a functional liquid for wiring pattern in which conductive fine particles such as metal fine particles are dispersed is placed directly in an area of the substrate in which a pattern is to be formed, and then is transformed to a conducting film pattern constituting a thin film by heat treatment or laser irradiation. This method has the following merits: a photolithography process becomes unnecessary; processes are substantially simplified; and a small amount of material is needed (see the related art example mentioned above, for example).
If a wiring pattern in which a plurality of materials are layered is formed by using the former wiring pattern formation method described above, for example, if a wiring pattern of a layered film with a two-layer structure is manufactured by using two kinds of material, a first functional liquid is placed and then baked so that a wiring pattern as a first layer (hereinafter referred to as a first layer wiring pattern) is obtained. Subsequently, a second functional liquid is placed on the first layer wiring pattern and then baked so that a second layer wiring pattern is obtained. Thus, the wiring pattern of a layered film with a two-layer structure has been formed. In this method, when the second layer wiring pattern is baked, the first layer wiring pattern is also baked. Namely, there is a difference in the hysteresis of heating between the first layer wiring pattern and the second layer wiring pattern. Avoid tends to occur inside the first layer wiring pattern due to the difference in the hysteresis of heating. Metal particles do not grow evenly because of the influence of the void, and as a result, the first layer wiring pattern is uneven. Affected by the unevenness, the layered film obtained after baking the second layer wiring pattern has the irregular thickness, and therefore securing flatness of the wiring pattern in the layered film is not enabled. The film has the possibility that quality problems such as a crack and a breakage will occur. If the wiring pattern of a layered film with a three-layer structure is formed by using three kinds of material, the similar tendency is acknowledged. As a result, the layered film with a three-layer structure has the irregular thickness, and securing flatness of the wiring pattern is more difficult. In summary, the more the number of layers of the film increases, the more the irregularity of the film thickness of the layered film increases.